JP2886379B2 - Injection mold for disk and method of manufacturing disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk injection molding die for injection molding a disk such as a video disk or a compact disk, and more particularly to a disk injection molding having a step between a hold portion and a recording portion. Regarding the mold.

[0002]

2. Description of the Related Art Conventionally, flat discs such as compact discs have been used as information carriers, and various injection molding dies for molding them have been known. On the other hand, mini discs have been used as discs of a new standard. The mini-disc has a shape in which the recording section having an information area and the holding section around the center hole provided for holding the disc by the reproducing apparatus are displaced along the axial direction, and the mini disc is provided between the recording section and the holding section. Because it has a step,
Molding with an injection mold suitable for a conventional flat disk has the following new problems.

[0003]

That is, in a conventional disk injection molding die as shown in a sectional view of the vicinity of the cavity in FIG. 10, the molten resin injected into the cavity 203 through the sprue hole 201 does not Then, the fluid flows from the position corresponding to the end surface 207 of the center hole of the disk 205 to be formed to the outer peripheral portion.

At this time, since the molten resin is oriented when flowing through the step 209, the step 2
In the vicinity of 09, the birefringence index deteriorates as shown in FIG. For comparison, FIG. 9 shows the birefringence of a disk having no step. In an optical disk, the birefringence is preferably as close to 0 as possible. If the birefringence deteriorates (increases from 0 to + or-side), it may hinder use as an optical disk. Had become a problem.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and in the injection molding of a disk having a step portion between a hold portion and a recording portion, for example, a mini-disc.
An object of the present invention is to provide an injection molding die for a disk capable of molding a disk having a good birefringence in the peripheral area of a step, and a method of manufacturing a disk by an injection molding machine having the die.

[0006]

In order to achieve the above object, the present invention has the following structure as means for solving the problems. That is, the injection molding die for a disk according to the first aspect comprises a fixed side die fixed to a fixed platen of an injection molding machine and a movable side die fixed to a movable platen. In a disk injection molding die provided with a disk-shaped cavity formed on the joint surface of the above, an injection hole provided in the fixed die and communicating with the cavity at the center of the cavity and serving as a passage for molten resin is formed. A fixed sleeve having a closed portion protruding into the cavity so as to form a step at the center of the disk, and a sliding portion having a core retaining function at the distal end, and a passage for the molten resin in the injection hole. A hot plunger slidably inserted into the injection hole by forming a space to be formed, and a disk in which the cavity is formed by the cavity-side end of the fixed sleeve and the closing portion. A gate is formed at a position corresponding to the inner peripheral edge of the recording portion, the gate allowing the molten resin to pass in a direction perpendicular to the inner peripheral edge, and controlling the flow of the molten resin into the cavity and the prevention thereof by opening and closing operations. It is characterized by the following.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a disk, comprising: using an injection molding machine having an injection mold for a disk according to the first aspect of the present invention; And injecting the molten resin into the cavity through the gate, and after substantially filling the cavity with the injected molten resin, starting closing the gate while continuing the injection of the molten resin, The injection pressure is maintained until the gate is completely closed.

[0008]

In the disk injection mold having the above-mentioned structure, the fixed mold and the movable mold are relatively moved and closed.
The mold is clamped at a predetermined mold clamping pressure, and a cavity for disc molding is formed between the joining surfaces. At this time, the gate is in the open state.

Subsequently, the molten resin is injected from the injection nozzle and flows into the cavity via the gate. The gate is provided at a position corresponding to the inner peripheral edge of the recording portion of the product disc so that the molten resin can pass in a direction perpendicular to the inner peripheral edge. Flows in two directions from the position corresponding to the inner peripheral edge of the recording section to the recording section and the hold section, and densely fills the cavity.

The molten resin from the position corresponding to the inner peripheral edge of the recording portion to the recording portion flows only in the direction along the disk surface and is not oriented. This prevents the birefringence from deteriorating due to the orientation of the resin in the recording portion on the outer periphery of the step portion. Since the hold portion on the inner peripheral side of the step portion is not used as an information area, there is no problem even if the birefringence is deteriorated by the orientation of the resin.

When the molten resin substantially fills the cavity, closing of the gate is started while continuing injection of the molten resin.
Until the closing of the gate is completed, the injection pressure for injecting the molten resin is maintained, and the injection of the molten resin is continued. Therefore, even if the apparent volume of the cavity increases with the closing of the gate, the molten resin continues to flow into the cavity until the gate is completely closed, thereby satisfying the increase in the apparent volume. For this reason, insufficient filling of the molten resin does not occur.

When the closing of the gate is completed, the flow of the molten resin into the cavity is stopped. After the flow of the molten resin into the cavity is stopped, the mold is clamped until the resin solidifies. After the resin in the cavity has solidified, the mold is opened and the product disc is removed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an injection molding die for a disk of the present invention and a method of manufacturing a disk using an injection molding machine provided with the die will be described in detail with reference to examples. 1 and 2
1 is a sectional view of a disk injection molding machine provided with a disk injection molding die according to one embodiment of the present invention.

The disk injection molding machine 1 provided with the disk injection molding die of the present embodiment has a fixed platen 7 fixed to a plurality of stays 3 with nuts 5 respectively, and slides along the stays 3. A disk-shaped cavity 11 is formed by pressing the movable plate 9 that is attached so as to be capable of being mounted, and a disk such as a mini disk having a step between a holding unit and a recording unit is formed. It is a device that can do it.

A fixing die 13 composed of a first fixing member 13a, a second fixing member 13b and a third fixing member 13c is attached to the fixing plate 7 by bolting not shown. Further, the first movable member 15a, the second movable member 15
The movable mold 15 composed of the third movable member 15b and the third movable member 15c is attached. A fixed mirror panel 17 and a movable mirror panel 19 are opposed to the joint surfaces of the two dies 13 and 15, respectively, also by bolting. The above-described cavity 11 is formed as a space between the opposed fixed side mirror board 17 and the movable side mirror board 19. Each of the mirror boards 17 and 19 is provided with a cooling groove 20.

First, the structure of the fixed mold 13 will be described. The fixed mold 13 has an inner cylindrical portion 21a and an overhang portion 21b, which is opened at the center of the fixed-side mirror surface plate 17, and a fixed sleeve 21 partially double-cylindrical includes a second fixed member 13
b and the third fixing member 13c so as to sandwich the overhanging portion 21b. An injection hole 31 is formed inside the fixed sleeve 21 at the inner wall 23. A space is formed between the double cylindrical inner cylinder portion 21a and the overhang portion 21b. A heater 2 is provided on the outer periphery of the inner cylindrical portion 21a.
4 a, the inside of the injection hole 31 can be heated via the fixed sleeve 21.

A stamper holder 25 penetrates through the fixed side mirror board 17 so as to be fitted on the fixed sleeve 21. One end of the stamper holder 25 slightly protrudes from the fixed-side mirror panel 17, and the other end is in contact with the overhang 21 b of the fixed sleeve 21. As shown in FIG. 3, the portion of the stamper holder 25 slightly projecting from the fixed-side mirror plate 17 is an inner peripheral portion of a stamper 27 attached to the fixed-side mirror plate 17 to form an information surface of a disk. Can be held. Further, the outer peripheral portion of the stamper 27 is sandwiched between an annular outer ring 28 attached to the outer peripheral portion of the fixed side mirror surface plate 17 and the fixed side mirror surface plate 17.

The stamper 27 has irregularities corresponding to the disk to be formed, and the irregularities are transferred to the information surface of the disk. Also, the cavity 11
To be more precise, it is formed in a disk shape between the cavity surface 19a of the movable mirror panel 19 and the stamper 27.

On the other hand, the projecting portion 2 of the stamper holder 25
The end from 1b is held by a holder retainer 29 provided through the third fixing member 13c so as not to be detached from the fixed mirror panel 17. The end of the fixed sleeve 21 opposite to the fixed-side mirror plate 17 is a sprue bushing 33.
And are effectively united. The sprue bushing 33 is fixed to the first fixing member 13a.

The sprue bushing 33 is provided with an inner hole 37 communicating with the injection hole 31, and one end of the inner hole 37 is opened at a concave nozzle contact surface 35 formed in the sprue bushing 33. doing. A heater 24 b is arranged on the outer periphery of the sprue bushing 33 so that the inside of the injection hole 31 can be heated via the sprue bushing 33.

Nozzle contact surface 3 of sprue bushing 33
5, the tip of an injection nozzle 39 attached to a feed device (not shown) is in close contact with the feed device. Injection nozzle 3
An injection path 41 is provided at 9 along the central axis. The injection path 41 communicates with the resin reservoir of the feed device, and the molten resin can be injected from the feed device via the injection path 41. The injection nozzle 39 can reciprocate in the axial direction according to the feed device, and can be separated from and abutted on the nozzle contact surface 35.

Further, a hot plunger 43 coaxial with the injection hole 31 is slidably inserted through the fixed sleeve 21 and the sprue bushing 33 in a direction along the axis of the injection hole 31. Cavity 11 of hot plunger 43
At the end on the side, a flange-shaped closing portion 45 having an outer diameter capable of closely contacting and sliding the inner wall 23 and capable of being housed in the injection hole 31 is provided. A gate is formed by the end of the fixed sleeve 21 on the cavity 11 side and the closing part 45. At the end of the hot plunger 43 on the side of the cavity 11, an insertion hole 47 having a circular cross section is provided on the end face. The closing portion 45 protrudes into the cavity 11 and forms a gate 48 through which the molten resin can pass between the fixing sleeve 21 and the fixed sleeve 21. When the gate 48 is housed in the injection hole 31, the closing portion 45 closes the injection hole 31 and establishes communication with the cavity 11. Cutting (gate cut) is possible.

A sliding portion 43a is formed from the other end of the hot plunger 43 to near the center. The sliding portion 43a has an outer diameter such that the sliding portion 43a is slidably fitted into the injection hole 31. The sliding portion 43a is provided with a resin passage 43b including a plurality of through holes.

Between the sliding portion 43a of the hot plunger 43 and the closing portion 45, the sliding portion 43a is connected to the sliding portion 43a.
A small diameter portion 43d having an outer diameter smaller than a is formed.
An annular space 43c through which the molten resin can pass is formed between the small diameter portion 43d and the inner wall 23. This annular space 43
c is in communication with the resin passage 43b and has an annular space 43c.
Is larger than the resin passage area of the resin passage 43b.

The above-described injection path 41, small-diameter hole 37, and injection hole 3
1. A space communicated with the resin passage 43b, the annular space 43c, the gate 48 and the cavity 11 is formed, and constitutes an injection path (hot runner) for the molten resin supplied from the feed device. Further, the sliding portion 43a is partially exposed at an opening formed in the fixed sleeve 21. The rod 53 penetrating through this opening is a sliding part 43a.
It is connected to. The rod 53 can reciprocate in the opening along the axial direction of the hot plunger 43. The rod 53 is connected to a gate cut cylinder 49.
The hot plunger 43 is reciprocally movable in accordance with the reciprocating motion of the gate cut piston 51 slidably inserted therein.

The gate cut cylinder 49 is provided with a hydraulic supply / discharge passage 50 for supplying hydraulic oil from a hydraulic supply device (not shown).
two oil chambers 49a, 4 which are supplied / discharged via a, 50b
9b, the gate cut piston 51 can reciprocate by supplying and discharging hydraulic oil.

Next, the structure of the movable mold 15 will be described. Behind the movable platen 9, a mold clamping ram 55 for moving the movable platen 9 forward and backward with respect to the fixed platen 7 is fixed by bolting. The mold clamping ram 55 is connected to a piston inserted into a mold clamping cylinder (not shown), and has a function of moving the movable platen 9 forward and backward along the stay 3. Thereby, the movable mold 15 is closed with respect to the fixed mold 13,
Each operation of mold clamping and mold opening can be performed.

The machine ejector 57 penetrates through the movable platen 9
Is provided. One end of the machine ejector 57 is connected to a piston 63 in a hydraulic cylinder 61, and is connected to two oil chambers 61 from a hydraulic supply device (not shown).
The machine ejector 57 can reciprocate in response to the movement of the piston 63 which reciprocates due to the supply and discharge of hydraulic oil to and from a and 61b.

The other end of the machine ejector 57 penetrates the first movable member 15a, and is connected to the ejector sleeve 65.
Abuts the rear end of the The ejector sleeve 65
The second movable member 15b, the third movable member 15c, and the movable mirror panel 19 are slidably inserted through the ejector bushings 67 provided through the third movable member 15c and the movable mirror panel 19. ing.

The distal end of the ejector sleeve 65 reaches the cavity 11, and has a flange portion 65a at the rear end. A spring 69 is disposed between the flange portion 65a and the eject bushing 67 so as to bias the flange portion 65a toward the first movable member 15a. The ejector sleeve 65 abuts the flange portion 65a against the first movable member 15a by the action of the spring 69, but when the flange portion 65a is pressed by the machine ejector 57, the ejector sleeve 65 advances against the spring 69 and moves forward in the cavity 11. It is possible to protrude. A spring 69 is housed in the second movable member 15b, and the ejector sleeve 65
Is formed so as to be able to reciprocate.

A tubular center rod 71 attached to the first movable member 15a is inserted through the ejector sleeve 65. The rear end of the center rod 71 is bolted to the first movable member 15a, and the front end is the cavity 11
The insertion hole 47 of the hot plunger 43 is inserted through the center of the hole.

Center rod 71, ejector sleeve 6
The ejector sleeve 65 and the ejector bushing 67 are concentric, and the ejector sleeve 65 can slide on the outer peripheral surface of the center rod 71 and the inner peripheral surface of the ejector bushing 67. Next, a case where a disk is molded by the disk manufacturing method according to the fourth embodiment using the disk injection molding machine 1 provided with the disk injection molding die of the present embodiment will be described. The stamper 27 corresponding to the disk to be molded is attached to the fixed mirror panel 17 via a stamper holder 25 and an outer ring 28 in advance.

First, the movable mold 15 is moved forward together with the movable platen 9 by the mold clamping ram 55, and abuts against the fixed mold 13 to close the mold.
Disc-shaped cavity 1 in a pressed state with a predetermined mold clamping pressure
1. This state is shown in FIG. At this time, the operation of the gate cut piston 51 causes the hot plunger 43
Protrudes as much as possible into the cavity 11 and forms a gate 48 between the closing part 45 and the fixed sleeve 21.
The degree of opening of the gate 48 (the distance between the closing portion 45 and the fixed sleeve 21) is such that the length of insertion of the center rod 71 into the insertion hole 47 is such that an appropriate amount of molten resin passes through the gate according to the disk to be molded. By the way, it is adjusted. An appropriate opening of the gate 48 is determined by a disk molding experiment or the like.

Next, the molten resin supplied from the feed device is injected into the injection nozzle 39 in close contact with the nozzle contact surface 35.
And the cavity 11 is filled through the inner hole 37, the injection hole 31, the resin passage 43b, the annular space 43c, and the gate 48. Heaters 24 a and 24 b are arranged in the hot runner, particularly on the outer periphery of the fixed sleeve 21 and the sprue bushing 33.
Since the molten resin inside is heated, the molten resin is maintained at an appropriate temperature even while passing through the hot runner.

Further, since the cross-sectional area of the annular space 43c is larger than the resin passage area of the resin passage 43b, the flow history received when the molten resin passes through the through hole forming the resin passage 43b is represented by an annular shape. It is released in the space 43c.
When the molten resin passes through, for example, a tubular or groove-like passage such as the resin passage 43b, a flow history corresponding to the cross-sectional shape of the passage is given. If this flow history is kept, for example, it becomes a petal shape corresponding to the cross-sectional shape of the resin passage 43b and flows and diffuses in the cavity 11,
The quality of the molded disc may be impaired. However, as described above, in the mold of this embodiment, the annular space 43
Since the flow history is released in step c, the problems described above are prevented, and a disc of good quality is formed.

The gate 48 is formed between the fixed sleeve 21 and the closing portion 45 at an extended surface of the outer peripheral surface of the closing portion 45, that is, at a position corresponding to the inner peripheral edge of the recording portion of the product disk. Resin fills cavity 11 with gate 48
, Flows in two directions from the outer periphery to the center, and densely fills the cavity 11.

The molten resin flowing from the gate 48 to the outer peripheral portion flows only in a direction perpendicular to the axis of the disk-shaped cavity 11, that is, in a direction from the step portion of the product disk to the outer peripheral portion, and is not oriented. This prevents the birefringence from deteriorating due to the orientation of the resin at the outer peripheral portion of the product disc formed by the resin flowing from the gate 48 to the outer periphery.

The resin flowing from the gate 48 to the center is
It is oriented to change the flow direction almost perpendicularly on the way,
Since the inner peripheral portion formed of this resin is not used as an information area, there is no problem even if the birefringence is deteriorated by the orientation of the resin. When the cavity 11 is substantially filled with the molten resin, the gate cut is started while the injection of the molten resin is continued.

The gate cut is started by supplying hydraulic oil to the lower oil chamber 49b of the gate cut cylinder 49 and discharging the hydraulic oil from the upper oil chamber 49a through the hydraulic supply / discharge passages 50a and 50b. It is done by adjusting. This adjustment is performed by a main controller (not shown). Specifically, the main controller determines that a predetermined time has elapsed from the completion of the mold clamping by using a timer, and controls driving of valves (not shown) of the hydraulic supply / discharge paths 50a and 50b. It should be noted that the timer is set with a time previously obtained at the time of trial production of a disk or the like.

Due to the supply and discharge of the hydraulic oil, the gate cut piston 51 moves toward the oil chamber 49b (upper side in the figure), and the hot plunger 43 connected to the gate cut piston 51 also moves in the same direction. The movement of the hot plunger 43 moves the closing portion 45 into the fixed sleeve 21 to close the injection hole 31 (FIG. 2). This prevents the gate from being cut and injecting more molten resin into the cavity 11.

At this time, as the closing portion 45 moves into the fixed sleeve 21, the apparent volume of the cavity 11 increases by the amount of the movement. However, since the injection pressure of the molten resin is maintained and the molten resin continues to flow into the cavity 11 until the gate cut is completed, the moving amount of the closing portion 45 is filled with the molten resin. Therefore, even if the apparent volume of the cavity 11 increases due to the movement of the closing portion 45, no problem occurs due to this.

The tip of the center rod 71 is inserted into the insertion hole 47 of the hot plunger 43 to prevent the hot plunger 43 from misaligning.
The movement along the axial direction is precisely done. Therefore, the closing portion 45 is accurately housed in the fixed sleeve 21 and closes the injection hole 31.

The center rod 71 and the cavity 11
It also has the effect of forming a central hole in the resin inside. In the conventional center hole opening method, the molten resin once filled in the center hole forming position is removed by, for example, a cutter punch projecting forward into the cavity to form a center hole. In the embodiment, since the center rod position is not filled with the resin because of the presence of the center rod 71, the difference from the first embodiment is that the center hole opening work is not required in the first place.

In this state of FIG. 2, the process waits for the resin to solidify. This also requires the solidification time required for disk prototypes,
The time is set in a predetermined timer of the main controller. When the solidification time has elapsed, the mold clamping ram 55 is retracted to bring the mold into an open state. FIG. 3 shows a state of the movable mirror panel 19 after the mold is opened.

When the mold opening is started, the solidified disk 10
0 peels off from the stamper 27. At this time, the inner periphery of the stamper 27 is held by the stamper holder 25, and the outer periphery of the stamper 27 is pressed and held by the fixed mirror panel 17 by the outer ring 28. That is,
The stamper 27 includes the stamper holder 25 and the outer ring 2.
At 8, it is held so as to be in close contact with the fixed mirror panel 17. Therefore, the disk 10 together with the movable mirror panel 19 is
When 0 is peeled off from the stamper 27, even if a force is applied to peel the stamper 27 from the fixed side mirror board 17 via the disk 100, the stamper 27 is held in close contact with the fixed side mirror board 17, In addition, it is protected from deformation due to the force of peeling.

In the state shown in FIG. 3, a solidified disk 100 is adhered to the surface of the movable mirror panel 19. Next, the supply and discharge of the hydraulic oil to and from the oil chambers 61a and 61b are adjusted so that the hydraulic oil is supplied to the lower oil chamber 61b of the hydraulic cylinder 61 and discharged from the upper oil chamber 61a. . This adjustment is also performed by each oil chamber 61 by the main controller.
The control is performed by driving and controlling a valve (not shown) of a hydraulic supply / discharge path to the a and 61b.

When the hydraulic supply / discharge control to the hydraulic cylinder 61 is executed, the piston 63 in the hydraulic cylinder 61 moves toward the oil chamber 61a in response to the control. At the same time piston 63
Is ejected from the first movable member 15a into the second movable member 15b, and presses the flange portion 65a of the ejector sleeve 65. Ejector sleeve 65 pressed against flange 65a
Moves forward and protrudes from the movable mirror panel 19, and the disk 1
00 is peeled from the movable mirror panel 19 (FIG. 4). The peeled-off disk 100 is taken out of the injection molding machine by an appropriate take-out means provided with a suction cup or the like.

As described above, according to the disk injection molding machine 1 of the present embodiment, the gate 48 for introducing the molten resin from the inner wall 23 to the cavity 11 is provided between the inner wall 23 and the closed portion 45 by the outer periphery of the closed portion 45. The molten resin flowing from the gate 48 to the outer peripheral portion is formed in an extended surface of the surface, that is, at a position corresponding to the inner peripheral edge of the recording portion of the product disk, in a direction orthogonal to the axis of the disc-shaped cavity 11, that is, It flows only in the direction from the step of the disk toward the outer circumference. Therefore, the flowing resin is not oriented by a step or the like. As a result, including the information area of the product disc,
In the recording portion on the outer periphery of the step portion, deterioration of the birefringence caused by the orientation of the resin is prevented.

Further, since the end of the center rod 71 is inserted into the insertion hole 47 of the hot plunger 43, the hot plunger 43 is prevented from being misaligned. Therefore, the movement of the hot plunger 43 in the axial direction is accurately performed along the central axis, and the movement of the closed portion 45 from the inner wall 23 is accurately performed. At the same time, since the center rod 71 limits the projecting distance of the hot plunger 43 into the cavity 11, the opening degree of the gate 48 (the closing portion 45 and the fixed sleeve 45) is determined by the insertion length of the center rod 71 into the insertion hole 47. 21
Distance) is adjusted. Therefore, an appropriate amount of molten resin passing through the gate according to the disk 100 to be molded is realized.

In the disk manufacturing method shown in this embodiment, when the cavity 11 is almost completely filled with the molten resin, the gate cut is started while the injection of the molten resin is continued. The gate cut is performed by moving the closing portion 45 into the fixed sleeve 21 to close the injection hole 31, and regulates the injection amount of the molten resin into the cavity 11 to an appropriate amount.

As the closing portion 45 moves into the fixed sleeve 21, the apparent volume of the cavity 11 increases by the amount corresponding to the movement. However, the injection pressure of the molten resin is not increased until the gate cut is completed. Is maintained and the molten resin continues to flow into the cavity 11, so that the closed portion 4
5 is filled with the molten resin.

Therefore, according to the disk manufacturing method shown in the present embodiment, even if the apparent volume of the cavity 11 becomes large due to the movement of the closing portion 45, no problem occurs due to this. In the present embodiment, the stamper is provided on the fixed-side mirror surface plate, but the stamper may be provided on the movable side according to the disk to be formed. Further, if air can be blown out from the movable side mirror surface and air is blown when the product disk is peeled off from the mirror surface disk, the product disk is further easily peeled off.

In this embodiment, the fixed sleeve 21
Although the sprue bushing 33 and the sprue bushing 33 are connected to be virtually integrated, they need not necessarily be integrated, and may be mounted as separate components. As described above, the present invention is not limited to such embodiments at all, and can be implemented in various modes without departing from the gist of the present invention.

[0054]

As described above in detail, according to the injection molding die for a disk and the method for manufacturing the disk of the present invention, the injection molding of a disk having a stepped portion between a holding portion and a recording portion, for example, a minidisk. In this case, it is possible to form a disk having a good birefringence in the peripheral area of the step.

Further, since the center hole is formed by the center rod, no operation for opening the center hole is required. Therefore, there is no occurrence of burrs and the like due to the operation, and it is possible to form a disk having a good center hole.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a disk injection molding die according to an embodiment when the die is closed.

FIG. 2 is a cross-sectional view when a gate is cut by a disk injection molding die according to an embodiment.

FIG. 3 is a partially enlarged cross-sectional view showing a state in which a molten resin is injected and filled into a cavity of the disk injection mold of the embodiment.

FIG. 4 is a partially enlarged cross-sectional view when the injection hole is closed in the disk injection molding die of the embodiment.

FIG. 5 is an explanatory view of the vicinity of the movable side mirror surface plate when the disk injection molding die of the embodiment is opened.

FIG. 6 is an explanatory view of the vicinity of a movable mirror surface plate when an ejector sleeve projects forward in a disk injection molding die according to an embodiment.

FIG. 7 is an explanatory diagram showing a birefringence of an information area of a disk molded by a disk injection molding die of an example.

FIG. 8 is an explanatory diagram showing a birefringence index of an information area of a disk having a step formed by a conventional disk injection molding die.

FIG. 9 is an explanatory diagram showing a birefringence index in an information area of a disk having no step formed by a conventional disk injection molding die.

FIG. 10 is an explanatory view showing the vicinity of a cavity of a conventional disk injection molding die.

[Explanation of symbols]

1. Injection molding machine for disk 3. Stay, 5.
..Nut, 7 ... Fixed board, 9 ... Movable board, 11.
..Cavity, 13: fixed mold, 15: movable mold, 17: fixed-side mirror faceplate, 19: movable-side mirror faceboard, 19a: cavity face, 20: cooling Groove 2
1 ... fixed sleeve, 21a ... inner cylinder part, 21b
..Overhangs, 23 ... Inner walls, 24a, 24b
・ Heater, 25 ・ ・ ・ Stamper holder, 27 ・ ・ ・ Stamper, 28 ・ ・ ・ Peripheral ring, 29 ・ ・ ・ Holder holder,
31 ... injection hole, 33 ... sprue bushing, 3
5 ... Nozzle contact surface, 37 ... Inner hole, 39 ... Injection nozzle, 41 ... Injection path, 43 ... Hot plunger, 43a ... Sliding part, 43b ... Resin Walkway, 4
3c: annular space, 45: closing portion, 47: insertion hole, 48: gate, 49: gate cut cylinder, 49a, 49b: oil chamber, 50a, 50b ...
・ Hydraulic supply / discharge path, 51 ... gate cut piston, 53
... Rod, 55 ... Clamping ram, 57 ... Machine ejector, 61 ... Hydraulic cylinder, 61a, 61b
... oil chamber, 63 ... piston, 65 ... ejector sleeve, 65a ... flange portion, 67 ... eject bushing, 69 ... spring, 71 ...
Center rod, 100: disk, 201: sprue hole, 205: disk, 207: center hole end face, 209: step portion,

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 45/26-45/44

Claims (4)

(57) [Claims] 1. A disk-shaped cavity formed on a joint surface when both dies are closed, comprising a fixed-side die fixed to a fixed platen of an injection molding machine and a movable-side die fixed to a movable platen. A fixed sleeve provided in the fixed mold and having an injection hole communicating with the cavity at the center of the cavity and serving as a passage for the molten resin; and a step at the center of the disk. A closing portion protruding into the cavity so as to form a portion at the tip portion, a sliding portion having a core-preserving action, and a space serving as a passage for molten resin in the injection hole; A hot plunger that is slidably inserted through the end of the fixed sleeve on the cavity side, and the closing portion, the position corresponding to the inner peripheral edge of the recording portion of the disk in which the cavity is formed. An injection molding metal for a disk, wherein a gate is formed, through which the molten resin can pass in a direction perpendicular to the inner peripheral edge, and which controls opening and closing operations of the molten resin into the cavity and preventing the molten resin from flowing into the cavity. Type. 2. A resin passage comprising a plurality of through holes is provided in said sliding portion of said hot plunger, and a small diameter portion is provided following said sliding portion, and said small diameter portion is provided between said small diameter portion and said fixed sleeve inner wall. By forming an annular gap communicating with the resin passage and having a cross-sectional area of at least the resin passage area of the resin passage, the flow history of the molten resin having passed through the through hole in the annular space can be released. 2. The method according to claim 1, wherein
An injection mold for a disk as described in the above. 3. A center having a tip for restricting the advance of the hot plunger and restricting the degree of opening of the gate when the mold is closed. 2. The movable plunger is provided coaxially with the hot plunger at a center portion of a cavity surface of the movable mold so as to protrude into the cavity so as to form a center hole in a disk to be formed. 2. The injection molding die for a disk according to 2. 4. A molten resin is injected from an injection nozzle into the cavity through the injection hole and the gate at a predetermined injection pressure by using an injection molding machine equipped with the disk injection molding die according to claim 1. After the cavity is substantially filled with the injected molten resin, the closing of the gate is started while continuing the injection of the molten resin, and the injection pressure is reduced at least until the closing of the gate is completed. A method for manufacturing a disk, comprising: maintaining the disk.